Relationship between the Cascadia fore-arc mantle wedge, nonvolcanic tremor, and the downdip limit of seismogenic rupture

McCrory, Patricia A.; Hyndman, R. D.; Blair, J. Luke

doi:10.1002/2013gc005144

Cited by 33 publications

(42 citation statements)

References 104 publications

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“…These features include the top of the subducting Juan de Fuca Plate, the slab Moho, a hydrated mantle wedge (where continental Moho and slab conversions are absent or weak), and the continental Moho. Furthermore, the positive arrival we interpret as the continental Moho (~5 s) is also within existing Moho depth estimates (~40-km depth) based on other data sets(McCrory et al, 2014). Within the depth estimate uncertainties of the top-of-slab(McCrory et al, 2012) and derived slab Moho, both dipping horizons are clearly seen in the stacked results(Figure 2c).…”

supporting

confidence: 88%

High‐Resolution Receiver Function Imaging Across the Cascadia Subduction Zone Using a Dense Nodal Array

Ward

Lin

Schmandt

2018

Geophysical Research Letters

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In the summer of 2017, we deployed 174 nodal geophones in the Cascadia Subduction Zone forearc with the specific aim of conducting a high‐resolution receiver function study. The dense trench perpendicular line in central Oregon with 500‐m spacing recorded continuous data for approximately 40 days. Our plate tectonic‐scale imaging results show the same features as previous broadband seismic deployments including the top of the subducting Juan de Fuca Plate, the slab Moho, and the continental Moho. Although our deployment was limited to around 40 days, the dense station spacing allowed us to image the shallow Oregon forearc in remarkable detail. In our shallow results, we image a continuous positive arrival that we interpret as the top of the accreted Siletzia terrane. We suggest that hybrid nodal/broadband deployments could be used in conjunction with offshore seismic studies to image subduction zones in unprecedented detail.

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supporting

confidence: 88%

High‐Resolution Receiver Function Imaging Across the Cascadia Subduction Zone Using a Dense Nodal Array

Ward

Lin

Schmandt

2018

Geophysical Research Letters

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“…The approximate location of the fore‐arc mantle corner is from McCrory et al . []. There is a gap of 50–100 km between the updip limit of slow slip and tremor and most estimates of the downdip limit of significant great earthquake rupture.…”

Section: Fore‐arc Mantle Corner: Aseismic Serpentinite and Talc On Thmentioning

confidence: 99%

“…An initial summary of constraints to the location of the fore‐arc mantle corner has been provided by McCrory et al . []. The accuracy is sufficient to show that the fore‐arc mantle corner is generally well landward of the seismogenic limit from most of the other constraints (e.g., Figure a).…”

Section: Fore‐arc Mantle Corner: Aseismic Serpentinite and Talc On Thmentioning

confidence: 99%

Downdip landward limit of Cascadia great earthquake rupture

Hyndman

2013

JGR Solid Earth

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[1] This paper examines the constraints to the downdip landward limit of rupture for the Cascadia great earthquakes off western North America. This limit is a primary control for ground motion hazard at near-coastal cities. The studies also provide information on the physical controls of subduction thrust rupture globally. The constraints are (1) "locked/ transition" zones from geodetic deformation (GPS, repeated leveling, tide gauges); (2) rupture zone from paleoseismic coastal marsh subsidence, "paleogeodesy"; (3) temperature on the thrust for the seismic-aseismic transition; (4) change in thrust seismic reflection character downdip from thin seismic to thick ductile; (5) fore-arc mantle corner aseismic serpentinite and talc overlying the thrust; (6) updip limit of episodic tremor and slip (ETS) slow slip; (7) rupture area associations with shelf-slope basins; (8) depth limit for small events on the thrust; and (9) landward limit of earthquakes on the Nootka transform fault zone. The most reliable constraints for the limit of large rupture displacement, >10 m, are generally just offshore in agreement with thermal control for this hot subduction zone, but well-offshore central Oregon and near the coast of northern Washington. The limit for 1-2 m rupture that can still provide strong shaking is less well estimated 25-50 km farther landward. The fore-arc mantle corner and the updip extent of ETS slow slip are significantly landward from the other constraints. Surprisingly, there is a downdip gap between the best other estimates for the great earthquake rupture zone and the ETS slow slip. In this gap, plate convergence may occur as continuous slow creep.

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“…Inversion on a profile for seismogenic locked zone and ETS locked zone between events (after Holtkamp and Brudzinski []), superimposed on map of the tremor and the fore‐arc mantle corner (after McCrory et al []), showing the excellent correspondence. The intervening zone on the thrust may exhibit longer‐term creep.…”

Section: The Location Of Etsmentioning

confidence: 99%

Cascadia subducting plate fluids channelled to fore‐arc mantle corner: ETS and silica deposition

et al. 2015

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In this study we first summarize the constraints that on the Cascadia subduction thrust, there is a 70 km gap downdip between the megathrust seismogenic zone and the Episodic Tremor and Slip (ETS) that lies further landward; there is not a continuous transition from unstable to conditionally stable sliding. Seismic rupture occurs mainly offshore for this hot subduction zone. ETS lies onshore. We then suggest what does control the downdip position of ETS. We conclude that fluids from dehydration of the downgoing plate, focused to rise above the fore‐arc mantle corner, are responsible for ETS. There is a remarkable correspondence between the position of ETS and this corner along the whole margin. Hydrated mineral assemblages in the subducting oceanic crust and uppermost mantle are dehydrated with downdip increasing temperature, and seismic tomography data indicate that these fluids have strongly serpentinized the overlying fore‐arc mantle. Laboratory data show that such fore‐arc mantle serpentinite has low permeability and likely blocks vertical expulsion and restricts flow updip within the underlying permeable oceanic crust and subduction shear zone. At the fore‐arc mantle corner these fluids are released upward into the more permeable overlying fore‐arc crust. An indication of this fluid flux comes from low Poisson's Ratios (and Vp/Vs) found above the corner that may be explained by a concentration of quartz which has exceptionally low Poisson's Ratio. The rising fluids should be silica saturated and precipitate quartz with decreasing temperature and pressure as they rise above the corner.

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Relationship between the Cascadia fore-arc mantle wedge, nonvolcanic tremor, and the downdip limit of seismogenic rupture

Cited by 33 publications

References 104 publications

High‐Resolution Receiver Function Imaging Across the Cascadia Subduction Zone Using a Dense Nodal Array

High‐Resolution Receiver Function Imaging Across the Cascadia Subduction Zone Using a Dense Nodal Array

Downdip landward limit of Cascadia great earthquake rupture

Cascadia subducting plate fluids channelled to fore‐arc mantle corner: ETS and silica deposition

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